Self-locking screw-thread.



c. WOODWARD. SELF LOCKING SCREW THREAD. APPLICATION FILED DEC- 21. 1916.

Patented Dec. 18, 1917.

WITNESS IRVING c. woonwnnn, or onroneo, rntmors.

SELF-L0 CKINQ- SQREW THREAD.

. Specification of Letters Patent.

asagna.

application filed December 21, 1916. Serial No. 138,168.

To all whom it may concern:

Be it known that I, IRVING C. WooDwARn,

a citizen of the United States of America, and a resident of Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Self-Locking Screw-Threads, of which the following is a specification.

The main objects of this invention are to provide an improved forni of thread for nuts, bolts, etc., which is self-locking and secures'the nut in any position on the bolt, regardless of pressure between the nut and the part which is to be retained in place on the bolt; to provide an improved thread for a nut which will retain the nut in its set position irrespective of oscillation or rotation of the member which is retained on the bolt; and to provide locking threads which are uniform in cross sectional area, of uniform pitch, and which may be cut by the vided, but as a general rule, such prior forms of threads known to applicant were usually a considerable departure in strength and design from the well lmown standard non-locking V threads, but when such standard forms of threads were made self-locking, it was common to eflect the latter pur-' pose by changing the pitch of the thread at different points on the nut or bolt or to distort the thread into a waveform, or to split the thread, or, rather, make a double thread which could be forced between the convolutions offa" true V thread, It is the purpose of the present invention to overcome certain objections to said prior forms of self-locking threads, such as weakening by cutting away too muchimetal or greatly distorting the same, and the further objection in the dif-v ficult "operations which are required to cut some such abnormal threads. v

- In the present design of thread, the interfitting or coacting threads on the nut or bolt are of exactly equal cross'sectional area as standard threads, and are formed to prothesame manner as do the standard forms of threads now commonly in use; The sole difference between thepresentinvention and x has Pam FEQQ Patented. nears, teat."

vide a snug fit along their entire surface' in a well known standard threads is that one member of a pair having coacting threads is provided with a thread the apex of which is slightly to oneside of the center or ofi'set so that when the nut is applied to the bolt,

such oflset portion will be forced back to form a trueV or resiliently engage the coacting thread and retain the nut in locked position.

In the drawings, a bolt 1 is provided with the well known formof v thread 2, while a i the nut 3 is provided with'athread 4 so cut as to be exactly equal in cross sectional area to the thread 2 on bolt 1, but with the apic'es 5 of the thread slightly o fi'set from a perpendicular passing through the center 1 1 of the base of the thread. Fig. 3 shows in",

full lines the shape of thread 4 and in broken lines 6 the position to which the apex of the thread is forced when the nut is secured on' to the bolt. 7 represents a line extending perpendicularly from the center of the .base of the thread, and this line passes through the center of apex 6 in the dotted position' thereof and clearly indicates that normally the apex of thethread is slightly to one side'of such center line.

The threads '2 and 4 are uniform in pitch," height and width at the base, and are also uniform in cross sectional area, thread 4' diii'ering'from thread 2 and other forms of threads in that the'apex of the thread is but slightly offset norinally. Fig 3 showsa slight exaggeration of such oflsetting.

It: will be understood that this invention may be a lipliedfl to threads having sharp, flat or roundedqa ices and that in all cases substantially that form generally approved and generally in \use and roviding'thesaine bearing area as the stan ard forms of threads.

When the-'nutisappliedto the bolt, the

thread 2. on the bolt forces the thread 4 to j exactly contformito the shape- 0f threadv 2- moving the apex 5 of' thread 4 from the 7 position in which is shown in full .passing through the athread of'uniform pitch, the apex formly to one side of a ing threaded portions, one member having.

a V-shaped thread of uniform pitch, the apex of said thread being slightly but uniperpendicular passing through the center of the base of the thread, the other member having a V-shaped thread of equal cross sectional area but the apex of which is on a perpendicular the thread.

2. A; device of the class described, comprising two members provided with coacting threaded portions, one member having of which is uniformly ofiset from a perpendicular passing through the center of the base of the thread, the other member havin a thread the apex of whichis ona perpen 1cular passing through the center of the base of the thread. q

- 3. Adevice of the class described, comprising two members provided with coactand center of the base of meant/ea ing threaded portions, said members having threads of uniform and equal pitch and of equal cross sectional areas, and said threads having diflerent sectional contours.

4. A device of the class described, comprising two members provided with coacting threads of uniform pitch and equal cross sectional areas, said threads having apices diderently located with respect to their respective bases. 5. A threaded member, the thread of which has sides extending at an angle of sixty degrees from'the base of the thread to approximately three-fourths its height, the remainder or apex of the thread being uniformly formed at different an les.

6. A threaded member, the threa of which has sides extending at equal angles from the base of the thread to approximately threefourths its height, the remainder 'or apex of the thread being uniformly formed at difl'er- 'ent angles.

7. A pair of complementary threaded members, one having a standard thread of equilateral triangular cross section, and the othe having a thread of equal cross sectional area and of like triangular form, except that a'limited part of its apex portion is uniformly distorted toward one side of a perpendicular passing through the center of its base.

Signed at Chicago this 18th day of December, 1916.

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